Screw-jack.



M. G. G/UMMING.

SCREW JACK.

APPLICATION FILED AUG.16, 1909.

Patented June 14,1910.

'prtof the s UNITED sTATEs PATENT OFFICE.

MILLARD C. CUMMING, 0F TIGEBBAY, FLORIDA', ASSIGNOR 0F ONE-HALF T0 L.W.`

COTTMAN, 6F TIGERBAY, FLORIDA. l

SCREW-J ACK.

To all whom itmay concern:

Be it known that I, MILLARD C. GUMMING, a citizen of the United States,residing Tigerbay, inthe county of Polk, State of Florida, have inventedcertain new and useful Improvements in Screw-Jacks; and I do herebydeclare the following to be a full, clear, 'and exact descriptionl ofthe invention, such as will enable'others. skilled in the artito whichit appertains to'make and use the same. V

. This invention relates to im rovements in liftingjacks and has foritso ject the provision of a device of that kind which may be extended to alen th substantially equal to twice the length o its supporting standardor base.

Another object is the provision of a stop serving to prevent the threadson the liftin sections from binding during the outwar or liftingmovement of one of the lifting sections.

With these and other objects in view as will more fully hereinafterappear, the resent invention'consists in certain nove details ofconstruction and arran ement of parts, hereinafter fully described,lllustrated 1n the accompanying drawin and more particularly pointed outin t 'ef-appended claims; it being understood 'that various cha in theform, roportion, size and minor details of the evice may be made withoutdeparting from the spiritor sacricing any ofthe advantages of theinvention.

In the accompanying drawings forming ification: Figure 1 isa sideelevation of t e device. Fig. 2 is a sectional view thereof. Fig. 3 is abottom plan view taken on the line 33 of Fig. 1 and showing one portionofythe toothed clutch.

ASimilar numerals of reference are employed to designate correspondingparts throughout.

The u right or base is designated in eny.eral by t e numeral 5 and isshown to. e a

'tubular structure interiorly screw threaded as shown atv 6. The outersurface of this upright or base is flared from its upper end and isprovidedf with the usual handle 7. The threads 6 extend for the entirelength i of the base 5 and engage with the exterlor threads of an innersection 8. TheY inner 4section 8 is screw threaded throughout its lengthcorresponds in length to the Specication of Lettersilatent. I

Application led August i6, 1909. Serial No. 513,199.

aty

imparted Patentedrime 14, 1910.

thickened head 9. The thickness of the head 9 corresponds approximatelyto one eighth the length of the inner section 8, and formed centrally ofthe head 9 is a threaded opening 10. The ,pitch of the threads in theopening 10 is the same as thepitch of the threads on the outer surfaceof the inner section 8 and inner surface of thesection 5, for a purposeto be presently described. The upper face of the head 9 1s flush withthe upper end of the section 8` and formed in the upper face are a pairof diametrically oppslte clutch teeth 11, which are adapted to engagewith a similar clutched surface to transmit movement to the section 8 inone direction only.

A second lifting section is designatedl in the length of thesection 8and its lower or inner end is provided with a head 15, the uppersurfaceV of which is provided with a "'palr of diametrically oppositeclutch teeth .17. Formed on the lower face of the head 9 are a pair-ofclutch teeth`18 similar to the clutch teeth 17 and which are adapted toengage with the latter when the head 15 is brought into engagement withthe head 9. The clutch teeth 17 and 18 are so formed that they willimpart movement to the section 8 in one direction only. The upper oropposite end of the shank 13 terminates in a lifting head 19, the up ersurface of which is fiat and the lower sur ace of which is provided witha pair of diametrically opposed Yclutch teeth 20, which are adapted Lto'engage with the clutch teeth 11 and imparta turning movement to thesection 8 inone direction only and opposite to the'mov'ement b theclutch teeth 17. Thehead 19 1s providled with a transverse opening 21,which is adapted to receive a suitable tool, by means of which the headmay be turned.

Having now described the structure of the .device its operation will begiven. The jack is laced in the Ordinar manner under the ob]ect to belii ed an la suitable bar or other tool is insel `ed through theopeningrQl '.in the lifting head 19. By turning the lat,-

ter in `one direction so that the bearing sur'- faces of the clutchteeth 20.011 the lower face of the head and the clutch teeth 11 on theupper face of the head 9 are moved into en-y gagement with each otherthe section 12 will ascend-on the threads of the opening 1Q in.

'the head After the section 12has asment ofthe section 8' on thethreads'6 that' thethreads 14 willbe prevented from bindcended t0 itsfull extent the clutch teeth 17 on the head 15 at the lower end of theshank will engage with the clutch teeth 18 on the lower face o fE thehead 8 whereby a 'rotary movement will beiimparted to the section' 8,which will cau'sethe latter to ascend on the thread 6 o-f the base 5. Itwill be observed that duringthe upward or outward moveingv "onfthethreads of the opening 10by virtue of the clutch teeth 17 and 18, sincethe bearing surfaces of these teeth will be in engagem ent` and willthereby prevent upward onpasending movement ofthe shank 13 on thethreads, ofthe opening 10 beyond a certain -point, so that when it isdesired to dis-' engage the jack from the object lifted the turningmovement of the head 19 in a direction to cause the section 12 todescend will not be prevented by the'threads binding.

It will be observed 'thatfthe device is exceedingly simple in Astructureand comparap tively inexpensiveto manufacture, and its utility will begreatly appreciated since with its use the employment of blocks, whichare. usually interposed between the lifting head and object to be liftedwhen 'devices of this kind having but one telescoping 'section are used,will not be necessary; for it is evident that after one section has beenextended to lits full extent and it is required to raise the tubularbasesection, a plurality of screw threaded telescoping sections threadedintol said base, one ofl said sections being provided with oppositelydisposed clutch surfaces 'and another of said sections lhaving similarlyformed clutch surfaces to engage with the clutch surfaces of thefirst-named lsection so as to cause the latter to ascend and descend onthe threads of the base section.

3'. In .a lifting jack, an interiorly threaded tubular` base section, alifting section threaded into said base and provided at its upper endwith a head having onits oppo-l site faces a plurality of clutch teeth,a third section threaded/'into the second section having heads at itsopposite ends the inner` faces ofwhich are provided with clutch teeth toengage with the teeth on the said second section so as to cause thelatter to ascend anddescend on-the threads of the base'section.

In testimony whereof, I alix my signature, in presence of two witnesses.

MILLARD C. CUMMING. Witnesses:

FRANK W. ZANDER,

W. ZANDER.'

